1. Field of the Invention
The present invention relates to a vehicle control device having a function of operating an automatic brake when an own vehicle is likely to collide with an obstacle and a function of operating an electric parking brake in response to an operation of a driver.
2. Description of the Related Art
Hitherto, there is known a device for operating an automatic brake when an own vehicle is likely to collide with an obstacle. For example, a driving support device proposed in Japanese Patent Application Laid-open No. 2015-49665 includes a clearance sonar for detecting a distance from an own vehicle to an obstacle, and is configured to determine whether or not the own vehicle is likely to collide with the obstacle based on the distance detected by the clearance sonar. When the own vehicle is determined to be likely to collide with the obstacle, a pump motor provided in a brake actuator is driven so that a pump rotates to increase a hydraulic pressure in a wheel cylinder. As a result, the automatic brake operates independently of absence/presence of a brake pedal operation of a driver, and the collision of the own vehicle and the obstacle with each other can thus be avoided. For example, when the driver is carrying out a garaging operation in a narrow parking space, and the own vehicle is likely to collide with a garage wall, the automatic brake operates, and consequently, the collision can be avoided.
Moreover, as a parking brake, there is known an electric parking brake (referred to as EPB) that does not require an operation force of the driver to pull a parking brake cable. For example, a vehicle braking control device proposed in WO 2011/158855 A1 is configured to drive a parking motor (referred to as EPB motor) provided in a caliper based on a switch operation of a driver, thereby pressing brake pads against a brake disc by a rotational force of the EPB motor. As a result, the driver can bring wheels into a lock state by a light switch operation.
Incidentally, the following problem occurs in a vehicle having the function of driving the pump motor to operate the automatic brake, and the function of driving the EPB motor to operate the EPB. For example, under a situation in which the driver is carrying out the garaging operation at a very low speed, when the vehicle approaches the garage wall or the like and the automatic brake is thus operated, the driver may simultaneously carry out the switch operation for operating the EPB.
When the pump motor and the EPB motor are started respectively, large currents temporarily flow from a battery to the pump motor and the EPB motor. This large current that temporarily flows is referred to as rush current. Therefore, when the pump motor and the EPB motor are simultaneously started, as shown in FIG. 7, period in which the rush currents flow through the pump motor and period in which the rush currents flow through the EPB motor overlap each other. The currents flow through the pump motor and the EPB motor from a common battery, and when the rush currents required for the start are caused to flow through both the motors, a terminal voltage of the battery greatly decreases.
When the terminal voltage of the battery decreases below the minimum drive voltage required for the respective functions, the respective functions stop. This problem can be solved by increasing power supply performance of the battery, but this solution consequently leads to increases in a cost, a vehicle weight, a battery installation space, and the like.